Roller compacted geopolymer concrete using recycled concrete aggregate

In this research mechanical characteristics of roller compacted geopolymer concrete (RCGPC) and roller compacted cement concrete (RCC) using 100% recycled concrete aggregate (RCA) were investigated and compared. The surface morphology and formation of chemical compounds of the selected RCGPC composite mixtures were also analyzed using Scanning electron microscopy (SEM), X-Ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). It was revealed from the investigation that the compressive strength of the RCGPC material was dependent on the mixture variables like the molar concentration of sodium hydroxide (NaOH), sodium silicate (Na2SiO3) to NaOH ratio (alkali activator), curing time and temperature, and dosage of fly ash. The experimental results depicted that the compressive strength, modulus of elasticity, and flexural strength of RCGPC composites varied in the range of 7.5 to 27.6 MPa, 16 to 46.8 GPa, and 2.1 to 3.8 MPa, respectively. While RCC using 12% ordinary cement yielded a compressive strength, modulus, and flexural strength of 18.9 MPa, 32.7 GPa, and 2.1 MPa, respectively. SEM, XRD, and FTIR analysis also revealed the formation of geopolymer compounds and their relative presence in the new composite based on the mixture variables. It is believed that the developed RCA based roller compacted geopolymer concrete could be used as an alternative material for pavement construction. (C) 2021 Elsevier Ltd. All rights reserved.